"Most birds likely just get a bit tipsy, and very few people would be able to pick them out as intoxicated," said Meghan Larivee, laboratory coordinator at the government agency Environment Yukon in Canada. "However, every now and then, some birds just overdo it."

Such was the case with several Bohemian waxwings (Bombycilla garrulus) that flew into Whitehorse, Yukon, this fall, and ended up in "drunk tanks" after bingeing on fermented berries of the rowan tree.

The birds were admitted to the territory's Animal Health Unit, a wildlife facility equipped with modified hamster cages in readiness for the influx of berry-seeking migrants.

While there's no Breathalyzer for birds, it's pretty clear the waxwings were flying under the influence, according to Larivee.

"They cannot coordinate their flight movements properly or at all, and they are unable to walk in a coordinated way," she said in an email.

The birds, who come in with juice-stained beaks, are checked for illnesses that might otherwise explain their groggy condition. They generally recover after a few hours, she said.

Less fortunate are those intoxicated birds that die in collisions with buildings—two such fatalities were recorded in Whitehorse this fall.

An Alcohol Problem

While there are numerous anecdotal reports of such incidents in North America and Europe, there have been few studies to show that alcohol is indeed the cause.

"We've had the odd report from people phoning us up and saying they've had a waxwing or waxwings dead under their window and things like that," Andrews said.

If you come across a live bird that appears drunk but uninjured, Andrews advises putting the animal in a cardboard box with some air holes for a few hours until they sober up and can be released.

Climate Change Effect?

But if outbreaks of insobriety aren't so unusual among berry-eating birds, might climate change make them even more frequent?

Though not an unusual fall phenomenon, freezing causes the berries to convert starches into sugars, while subsequent thawing makes it possible for yeast to get in and speed up the fermentation process, Larivee explained.

Larivee's recent waxwing patients were admitted to her Yukon animal unit following several frosts and thaws due to warmer temperatures. Average global surface temperature increased 1.5 degrees Fahrenheit (0.85 Celsius) from 1880 to 2012, according to the Intergovernmental Panel on Climate Change.

While these effects are most pronounced in winter, "we also likely have longer autumns, which gives more time for berries to ferment, but still have early frost that allow sugars to be produced in berries early in the fall," she said.